EXCITOTOXICITY AND REPAIR OF COCHLEAR SYNAPSES AFTER NOISE-TRAUMA INDUCED HEARING-LOSS

GUINEA-PIGS were exposed to a traumatic sound inducing up to 80 dB hea ring loss. Beside the well described mechanical damage to outer hair c ells, a total disruption of inner hair cell (IHC)-auditory nerve synap ses was acutely observed within the traumatized area. To test the hypo thesis that synaptic damage is due to an excessive release of glutamat e by the IHCs, we examined the protective effect of the glutamate anta gonist kynurenate on noise-induced hearing loss. The high degree of pr otection observed with kynurenate attests that dendritic damage is an important component in noise-induced hearing loss. Moreover, we demons trate that a synaptic repair mechanism occurring within the first few days post-exposure is partly responsible for the recovery of temporary threshold shifts after an acoustic trauma. (C) 1998 Rapid Science Ltd .